The present invention relates to a consumed electric power reducing system and a consumed electric power reducing method at a starting time of a disk device such as a magnetic disk and, more particularly, a power supply control system and a power supply control method to be mounted on the JBOD (Just a Bunch of Disks). Here, the JBOD is a disk system in which a plurality of disk devices are assembled in one casing so that the assembly is used as a handling unit.
In the prior art, the power supply control system of this kind is used in a power source device which is employed commonly in a plurality of hard disk drives (as will be called the “HDD”).
FIG. 1 is a block diagram showing one example of a power supply control system of the prior art for the JBOD. This JBOD 20 is connected with a host system 21. The JBOD 20 includes a main power source unit 1, a DC voltage generating circuit 2, a control circuit 3 and a power supply circuit 4. The main power source unit 1 supplies the DC voltage generating circuit 2 with an AC voltage. The DC voltage generating circuit 2 generates a DC voltage from the AC voltage which is supplied from the main power source unit 1. The DC voltage thus generated by DC voltage generating circuit 2 is supplied to the power supply circuit 4. The host system 21 sends a command to the control circuit 3 through an interface 22. The control circuit 3 controls the power supply to HDDs 51 to 52 by sending a power supply circuit signal s1 to the power supply circuit 4.
Here will be described the HDD starting method which is generally utilized. In general, there are two HDD starting methods, which can be interchanged by setting the HDD.
According to a first starting method, when the HDD is supplied with the electric power, it is brought into a standby state by starting all other than the spindle motor (as will be called the “SPM”), and the SPM is raised with a command from the host system 21.
According to a second starting method (as will be called the “ordinary start”), when the HDD is supplied with the electric power, it is ordinarily started without any command from the host system 21.
Here will be described the operations. The JBOD 20 is also started by two starting methods employing the function of the HDD.
According to a first method, when the main power source unit 1 of the JBOD 20 is turned ON, the AC voltage is supplied from the main power source unit 1 to the DC voltage generating circuit 2, in which it is converted into the DC voltage. The converted DC voltage is fed to the power supply circuit 4. And, a command is sent from the host system 21 through the interface 22 to the control circuit 3 to start the individual HDDs 51 to 52 one by one. In accordance with the command received, the control circuit 3 sends the power supply circuit signal s1 to the power supply circuit 4. As a result, the SPMs in the HDDs 51 to 52 are sequentially started at the time interval which is designated by the host system 21. According to the first method, the HDDs 51 to 52 are so set that they may be started with the command from the host system 21.
According to a second method, when the main power source unit 1 of the JBOD 20 is turned ON, the AC voltage is supplied from the main power source unit 1 to the DC voltage generating circuit 2, in which it is converted into a DC voltage. This converted DC voltage is supplied to the power supply circuit 4. And, the electric power is supplied as it is from the power supply circuit 4 to all the HDDs 51 to 52 in the JBOD 20 thereby to start the SPMs simultaneously. In this second method, the HDDs 51 to 52 are so set that they are automatically started in an ordinary manner when supplied with the electric power.
However, the first and second methods thus far described have the following problems. The plurality of HDDs may be connected with the host system which does not have a function to be started with the command. In this case, the setting of the plurality of SPMs in the HDDs is made such that the SPM is automatically started after the electric power was supplied, thus causing the following problem. When the plurality of SPMs are automatically started, the consumed electric current increases to require a power source device of a high capacity. This is because the consumed electric power of the SPM takes the maximum at the starting time and because the plurality of SPMs in the JBOD are simultaneously started.